The present invention relates to an image display apparatus capable of enlarging and displaying an image produced by an image display device as an image generator on a screen by using optical parts including a projection lens, and an optical projector to be used in combination with the image display apparatus.
Recently, the so-called pixel-selection type image modulators, such as liquid crystal panels, have become prevalently used instead of projection cathode-ray tubes as image generators for projection image display apparatus. The image modulator, for example, forms an image by modulating light emitted by a light source, such as a mercury lamp, for each pixel. The effective screen size of the image modulator is as small as about 1 inch. The image modulator emits light closer to collimated light than that emitted by a projection cathode-ray tube. Therefore, a projection lens to be incorporated into the image modulator is small and has a large f-number, which is the ratio of the lens's focal length to the lens's maximum effective diameter. If the incident light on the lens is nearly collimated light, the speed of the lens is high even if the effective diameter D of the lens is small.
If the effective screen size of the image generator is small and the effective diameter D of the projection lens is small, image disturbance generally called speckle noise (scintillation) occurs; that is, the projection image display apparatus employing the image modulator is liable to generate speckle noise. Techniques intended to reduce speckle noise are disclosed in, for example, Japanese Patent Laid-Open Nos. 2001-228547 (Reference 1), Hei 7-168282 (Reference 2) and Hei 11-38512 (Reference 3).